The inspection and adjustment of the valve clearance in an automobile is very important particularly with regard to environmental pollution which is caused by exhaust gasses. Moreover, the inspection and adjusting of the valve clearance has in the past required a considerable amount of time and labor, and has had to be performed by persons skilled in this particular area. In order to detect when the piston is at the top dead center position, a crank lever has traditionally been rotated by hand, however, since modern automobiles are in most cases equipped with a cooling pump, a power steering pump, a supercharger and the like in the engine compartment, the above-described cranking operation becomes very difficult because of the small amount of space remaining in the engine compartment. Moreover, the above-described equipment is connected to the crank shaft so that, in trying to rotate the crank shaft by hand, a great amount of force is required and frequently results in the person turning the crank injuring himself due to slipping of his hand. The disadvantages of prior art detecting methods having been described, the objects of the present invention will now be defined.